At Craigie on Main in Cambridge, the perfect hamburger is cooked at 100 degrees for 90 minutes in a special oven before being seared and slathered in cheese.

At White Manna in Hackensack, N.J., the perfect burger is 2 ounces of beef sizzled on a griddle and then smashed flat on a steaming pile of onions.

Maybe the best burger is slathered in American cheese. Or infused with chopped bacon. Or ground from brisket and bone marrow.

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In truth, all of that or none of that can work just fine. So what exactly makes the humble hamburger — staple of the American menu, spawner of a million variations — so good? At the Somerville Theatre last week, science took a crack at that question.

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Working their way from bun to bun, the editors of a new science-focused digital project from America’s Test Kitchen took apart the ingredients in and cooking concepts behind the hamburger.

“We are on a quest to find the perfect burger,” said Molly Birnbaum, author and executive editor of Cook’s Science.

Sure, but who isn’t?

Within grazing distance of the stage in Davis Square, you can find the Foundry’s Foundry burger, ground from brisket chuck and short rib; Five Horses Tavern’s Tavern burger, an 8-ounce grass-fed beef patty topped with fried onion strings and “dirty cheese sauce”; Rosebud American Kitchen’s griddled cheeseburger, with a house beef blend and toppings that approach the Platonic ideal; and Boston Burger Company’s endless burger options, with a list of toppings — deep-fried mac and cheese, pulled pork, peanut butter — longer than this sentence.

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Those are just the places that I noticed while I was looking for parking. Davis Square will get a Five Guys as soon as there aren’t 500 guys selling burgers there.

Few of those 500, though, have put in as much thought and experimentation as Birnbaum and Dan Souza, another Cook’s Science executive editor.

What does your lettuce sound like? How do dense mashed potatoes make hamburger buns more fluffy? Why do younger cheeses melt so much more elegantly than those that are aged?

“Science has always been a part of our recipe development,” said Bridget Lancaster, one of two cohosts of the “America’s Test Kitchen” television show, replacing Christopher Kimball. “It’s so much better to tell you why things are happening.”

Over the course of a lively 90-minute show, Birnbaum and Souza dissected their version of patty perfection. So how do you achieve it at home?

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Start at the top: The potato bun, they declared, is unparalleled. And it turns out the airy buns at Flat Patties, in Harvard Square have long been a Test Kitchen creation, relying on starch from the mashed potatoes to inhibit gluten formation — resulting in a more tender bread. (Shake Shack uses Martin’s potato rolls.)

Tomatoes can be a risky proposition. Supermarket tomatoes hosed down with ethylene gas to ripen them quickly for sale may have the color, but won’t often have the deep umami flavor that an in-season tomato should lend. If tomatoes aren’t in season, skip ’em — that’s what Craigie on Main chef Tony Maws does.

Onions can be a polarizing addition, and too much — or even a tiny amount of the wrong onion — can overpower a burger. So how do you pick the right one? Well, the cellular composition of onions causes them to release smell and flavor when they’re manipulated. More cuts equal more onion flavor, and the same is true of bruises.

“If it smells like an onion, don’t buy it,” Souza explained, “because that means it’s been dropped, it’s been mishandled in some way.”

But if you’re one of those people who likes a thick slice of raw onion stacked atop the beef, then do whatever you want, I guess. It’s your funeral, which is fitting since your breath will smell like death.

Birnbaum and Souza declared American processed cheese to be the perfect burger addition for its “meltability.” But if you can’t stomach the idea of picking up a loaf of individually wrapped yellow cheese-ish slices, look for a block of cheddar — or anything else — that has not been aged more than a few months. In a Test Kitchen experiment, a slice of young cheddar melted gracefully in the oven, while an 18-month aged cheddar fell apart into a gloopy, oily mess.

A splash of ketchup is critical, of course. Heinz ketchup, Birnbaum declared, is the perfect food because it melds all five flavors — sweet, salty, sour, bitter, and umami — into a paste that nearly any American can instantly identify (an onstage taste test bore this out).

But the real secret to a satisfying burger is the beef. Store-bought ground beef is often ground too fine — the connective fibers in the meat sheared so often that the result is nearly a paste. Though it’s somewhat counterintuitive, the result is a denser, more rubbery burger. Beef ground at home in the food processor — cut a chuck roast into cubes, freeze them for about an hour, and then pulse into small morsels — can be formed into a looser, more succulent patty.

That all sounds great, you might be thinking, but how do you make the perfect turkey burger?